Preparation of modified zeolites and their utilization

ABSTRACT

A modified ZSM-5 type zeolite is provided by treatment of a ZSM-5 type zeolite with BF 3 . The novel product is characterized by reduced pore size and enhanced shape-selectivity, or by enhanced activity, or by both. This invention also provides a process for catalytically converting organic compounds by use of the novel composition, an illustrative conversion being the catalytic conversion of methanol to hydrocarbons.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of Ser. No. 526,764, filed Aug. 26, 1983,which in turn is a continuation of Ser. No. 355,419 filed Mar. 8, 1982,now both abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is concerned with the catalytic conversion ofhydrocarbons and other organic compounds over crystallinealuminosilicate zeolites of the ZSM-5 type which have been modified bytreatment with BF₃, to provide enhanced selectivity, activity, or both,and with the method for preparing such catalysts.

2. Description of the Prior Art

Zeolitic materials, both natural and synthetic, have been demonstratedin the past to have catalytic properties for various types ofconversions. One such conversion which has generated considerableinterest is the production of hydrocarbons, including olefins andgasoline from alcohols and ethers.

U.S. Pat. No. 4,025,575 describes a process by which lower alcoholsand/or their ethers are converted to a mixture of C₂ -C₅ olefins bycontact at subatmospheric inlet partial pressure with a crystallinealuminosilicate zeolite of the ZSM-5 type.

U.S. Pat. No. 3,931,349, issued Jan. 9, 1976, also discloses a processfor the conversion of methanol to gasoline utilizing a ZMS-5 typecatalyst.

U.S. Pat. No. 4,083,888, issued on Apr. 11, 1978, discloses a processfor the manufacture of hydrocarbons by the catalytic conversion ofmethanol in the presence of a substantially anhydrous diluent and aZSM-5 type zeolite.

There are many other patents and publications which describe theconversion of methanol to hydrocarbons, including gasoline, such as U.S.Pat. No. 3,931,349; 3,969,426; 3,899,544; 3,894,104; 3,904,916; and3,894,102, the disclosures of which are incorporated herein byreference. Other conversions include, for example, propyleneoligomerization, toluene disproportionation, xylene isomerization,alkylation of aromatics with alcohol or olefins, such astoluene+ethylene--p-ethyltoluene, and dewaxing, i.e., shape-selectivecracking of wax molecules.

U.S. Pat. No. 4,163,028 discloses the isomerization of a feedstockcontaining xylene in the presence of ZSM-5. U.S. Pat. No. 4,268,420describes a crystalline borosilicate AMS-1B (ZSM-5) which can be used asa catalyst in the isomerization of xylene.

U.S. Pat. No. 4,292,457 discloses the alkylation of aromatichydrocarbons in the presence of a borosilicate AMS-1B (ZSM-5) catalyst.U.S. Pat. No. 4,269,813 discloses the use of this catalyst indisproportionation and transalkylation processes as well as in xyleneisomerization. Similar processes in the presence of ZSM-4 and ZSM-5catalysts are also disclosed in U.S. Pat. No. 4,377,502.

U.S. Pat. No. 4,208,305 and U.S. Pat. No. 4,238,318 disclose, inaddition to the above catalytic processes, upgrading cracked gasolineand naphtha, preparation of olefins from alcohols, preparation ofolefinic gasoline, alkylation of olefins, separation of hydrogenmixtures, and catalytic hydrodewaxing of hydrocarbon oils in thepresence of zeolite catalysts.

All of the foregoing patents are incorporated herein by reference.

SUMMARY OF THE INVENTION

It has now been found that a ZSM-5 type zeolite is advantageouslymodified by contacting the zeolite with gaseous anhydrous borontrifluoride at moderately elevated temperature, such as 150° C., and fora relatively short time, such as 30 minutes, as more fully describedhereinbelow. Surprisingly, the novel product exhibits reduced activityfor cracking a refractory hydrocarbon such as normal hexane, as measuredby the alpha test conducted at 538° C., but it exhibits enhancedactivity for the conversion of methanol to hydrocarbons, as more fullydescribed hereinbelow. Furthermore, as will be shown by example, thenovel modified zeolite catalysts in general show a much higher catalyticactivity for conversions of less refractory feedstocks than normalhexane than would be expected from their alpha values. Such catalyticconversions of organic compounds include olefin oligomerization, toluenedisproportionation, xylene isomerization, catalytic dewaxing, and thecoversion of methanol to hydrocarbons, including olefins and/orgasoline.

The boron trifluoride treated zeolite catalyst makes it possible to uselower operating temperatures or, quite obviously, to use the sametemperatures as generally employed in the prior art but at higher spacevelocities. It is immediately apparent that having a catalyst ofenhanced activity has the potential for lowering operating costs due tothe fact that lower temperatures can be used and allowing for a greaterthroughput due to the fact that higher space velocities can be employed.

The treatment with boron trifluoride by the method described alsoimparts changes in chemical composition and physical properties as wellas catalytic properties. These are illustrated by Example 21. Thisexample suggests that a reaction occurs between the zeolite and BF₃. Italso demonstrates that the modified zeolites have somewhat smaller poresand therefore will favor formation of "thinner" molecules such asethylene (in methanol conversion) and para-xylene (in xyleneisomerization).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The novel catalyst of this invention is prepared simply by treating aZSM-5 type zeolite at least partially in the acid form, preferablyHZSM-5, with boron trifluoride. The treated zeolite preferably is purgedto remove any excess BF₃ that may be present. The method of treatment isnot narrowly critical and typical conditions utilize boron trifluorideflowing at 30 cc/min. through a 1 gram catalyst bed maintained at 150°C. However, it is noted that flow rates of 1 to 600 cc/min. through 1gram of catalyst bed maintained at a temperature of from 25° to 500° C.are also operable to produce the enhanced catalyst of this invention.The time at which the boron trifluoride is contacted with the catalystis also not narrowly critical and activation can be obtained at periodsof time ranging from 0.01 hour to 10 hours and preferably from about 0.1to 2.0 hours. Following treatment with boron trifluoride, the catalystis ready for use, but it may be air calcined, if desired. Contactingwith boron trifluoride is highly effective at atmospheric pressure, butsubatmospheric or elevated pressure may be used.

The conversion of lower alcohols, their ethers, or mixtures thereof toC₂ -C₅ olefins and to heavier hydrocarbons and the conversion ofmethanol to olefins, to gasoline, and to other hydrocarbons with ZSM-5type catalyst is well known. The conditions for these reactions are welldocumented in the patents incorporated herein by reference. The modifiedzeolites of this invention are advantageously used in these conversions.Other conversions in which the modified zeolites are advantageously usedwill now be described.

Oligomerization and polymerization involve the linking of similarmolecules in the presence of heat and a catalyst to form biggermolecules. Oligomerization involves the forming of dimers, trimers andquatramers, whereas a typical polymerization concerns the joining oflight olefins to form a very long chain olefin. Olefin oligomerizationand polymerization conditions include a temperature of from about 95° toabout 935° F., preferably form about 390° F. to about 810° F., apressure of from about atmospheric to about 10,000 psig, preferably fromabout atmospheric to about 2,000 psig, a WHSV (when a flow operation) offrom about 0.1 hour⁻¹ to about 50 hour⁻¹, preferably from about 0.5hour⁻¹ to about 10 hour⁻¹, and a contact time (when a batch operation)of from about 0.1 hour to about 48 hours, preferably from about 0.5 hourto about 24 hours and a hydrogen/olefin mole ratio of from about 0 toabout 20, preferably from about 0 to 10.

Olefin oligomerization, e.g., propylene may be carried out attemperatures below 525° C. and preferably at about 300° C., at WHSV'sfrom 0.1 to 50, preferably at about 30, at pressures from 350 psig to550 psig.

Toluene disproportination is carried out at temperatures from 90° C. to550° C., preferably at about 500° C., at pressures from 0 psig to 3000psig, at WHSV's from 0.01 hour⁻¹ to 90 hour⁻¹, preferably at about 10.

Xylene isomerization may be carried out at temperatures from 230° C. to540° C., more preferably from 230° C. to 300° C., at pressures up to1500 psig, preferably from 20 to 400 psig, at WHSV's from 0.1 to 200,preferably from 0.5 to 50, and more preferably from 5 to 25, and evenmore preferably at about 10.

As is known in the art, ZSM-5 type zeolitic materials are members of anovel class of zeolites that exhibit unusual properties. Although thesezeolites have unusually low alumina contents, i.e. high silica toalumina ratios, they are very active even when the silica to aluminaratio exceeds 30. The activity is surprising since catalytic activity isgenerally attributed to framework aluminum atoms and/or cationsassociated with these aluminum atoms. These zeolites retain theircrystallinity for long periods in spite of the presence of steam at hightemperature which induces irreversible collapse of the framework ofother zeolites, e.g. of the X and A type.

An important characteristic of the crystal structure of this class ofzeolites is that it provides constrained access to and egress from theintracrystalline free space by virtue of having an effective pore sizeintermediate between the small pore Linde A and the large pore Linde X,i.e. the pore windows of the structure have about a size such as wouldbe provided by 10-membered rings of oxygen atoms. It is to beunderstood, of course, that these rings are those formed by the regulardisposition of the tetrahedra making up the anionic framework of thecrystalline aluminosilicate, the oxygen atoms themselves being bonded tothe silicon or aluminum atoms at the centers of the tetrahedra. Briefly,the preferred type zeolites useful in this invention possess, incombination: a silica to alumina mole ratio of at least about 12; and astructure providing constrained access to the crystalline free space.

The silica to alumina ratio referred to may be determined byconventional analysis. This ratio is meant to represent, as closely aspossible, the ratio in the rigid anionic framework of the zeolitecrystal and to exclude aluminum in the binder or in cationic or otherform within the channels. Although zeolites with a silica to aluminaratio of at least 12 are useful, it is preferred to use zeolites havinghigher ratios of at least about 30. Such zeolites, after activation,acquire an intracrystalline sorption capacity for normal hexane which isgreater than that for water, i.e. they exhibit "hydrophobic" properties.It is believed that this hydrophobic character is advantageous in thepresent invention.

The preferred zeolites useful in this invention have an effective poresize such as to freely sorb normal hexane. In addition, the structuremust provide constrained access to larger molecules. It is sometimespossible to judge from a known crystal structure whether suchconstrained access exists. For example, if the only pore windows in acrystal are formed by 8-membered rings of oxygen atoms, then access tomolecules of larger cross-section than normal hexane is excluded and thezeolite is not of the desired type. Windows of 10-membered rings arepreferred, although in some instances excessive puckering of the ringsor pore blockage may render these zeolites ineffective. 12-memberedrings usually do not offer sufficient constraint to produce theadvantageous conversions, although the puckered 12-ring structure of theTMA offretite shows constrained access. Other 12-ring structures mayexist which, due to pore blockage or to other cause, may be operative.

Rather than attempt to judge from crystal structure whether or not azeolite possesses the necessary constrained access to molecules largerthan normal paraffins, a simple determination of the "Constraint Index",or C.I., as herein defined may be made by passing continuously a mixtureof an equal weight of normal hexane and 3-methylpentane over a smallsample, approximately one gram or less, of zeolite at atmosphericpressure according to the following procedure. A sample of the zeolite,in the form of pellets or extrudate, is crushed to a particle size aboutthat of coarse sand and mounted in a glass tube. Prior to testing, thezeolite is treated with a stream of air at 1000° F. for at least 15minutes. The zeolite is then flushed with helium and the temperature isadjusted between 550° F. and 950° F. to give an overall conversionbetween 10% and 60%. The mixture of hydrocarbons is passed at 1 liquidhourly space velocity (i.e. 1 volume of liquid hydrocarbon per volume ofzeolite per hour) over the zeolite with a helium dilution to give ahelium to total hydrocarbon mole ratio of 4:1. After 20 minutes onstream, a sample of the effluent is taken and analyzed, mostconveniently by gas chromatography, to determine the fraction remainingunchanged for each of the two hydrocarbons.

The C.I. is calculated as follows: ##EQU1##

The Constraint Index approximates the ratio of the cracking rateconstants for the two hydrocarbons. Zeolites suitable for the presentinvention are those having a Constraint Index of 1 to 12. C.I. valuesfor some typical zeolites are:

    ______________________________________                                        CAS                 C. I.                                                     ______________________________________                                        ZSM-4               0.5                                                       ZSM-5               8.3                                                       ZSM-11              8.7                                                       ZSM-12              2                                                         ZSM-23              9.1                                                       ZSM-35              4.5                                                       ZSM-38              2                                                         TMA Offretite       3.7                                                       Beta                0.6                                                       H--Zeolon (mordenite)                                                                             0.4                                                       REY                 0.4                                                       Amorphous Silica-Alumina                                                                          0.6                                                       Erionite            38                                                        ______________________________________                                    

The above-described Constraint Index is an important and even criticaldefinition of those zeolites which are useful in the instant invention.The very nature of this parameter and the recited technique by which itis determined, however, admit of the possibility that a given zeolitecan be tested under somewhat different conditions and thereby havedifferent Constraint Indexes. Constraint Index seems to vary somewhatwith severity of operation (conversion) and the presence or absence ofbinders. Therefore, it will be appreciated that it may be possible to soselect test conditions to establish more than one value in the range of1 to 12 for the Constraint Index of a particular zeolite. Such a zeoliteexhibits the constrained access as herein defined and is to be regardedas having a Constraint Index of 1 to 12. Also contemplated herein ashaving a Constraint Index of 1 to 12 and therefore within the scope ofthe novel class of highly siliceous zeolites are those zeolites which,when tested under two or more sets of conditions within theabove-specified ranges of temperature and conversion, produce a value ofthe Constraint Index slightly less than 1, e.g. 0.9, or somewhat greaterthan 12, e.g. 14 or 15, with at least one other value of 1 to 12. Thus,it should be understood that the Constraint Index value as used hereinis an inclusive rather than an exclusive value. That is, a zeolite whentested by any combination of conditions within the testing definitionset forth here-inabove and found to have a Constraint Index of 1 to 12is intended to be included in the instant catalyst definition regardlessthat the same identical zeolite tested under other defined conditionsmay give a Constraint Index value outside of 1 to 12.

The class of zeolites defined herein is exemplified by ZSM-5, ZSM-11,ZSM-12, ZSM-21, ZSM-23, ZSM-35, ZSM-38, ZSM 48, and other similarmaterials. U.S. Pat. No. 3,702,886 describing and claiming ZSM-5 isincorporated herein by reference.

ZSM-11 is more particularly described in U.S. Pat. No. 3,709,979, theentire content of which is incorporated herein by reference.

ZSM-12 is more particularly described in U.S. Pat. No. 3,832,449, theentire content of which is incorporated herein by reference.

ZSM-21 is more particularly described in U.S. Pat. No. 4,046,859, theentire content of which is incorporated herein by reference.

ZSM-23 is more particularly described in U.S. Pat. No. 4,076,842, theentire content of which is incorporated herein by reference.

ZSM-35 is more particularly described in U.S. Pat. No. 4,016,245, theentire content of which is incorporated herein by reference.

ZSM-38 is more particularly described in U.S. Pat. No. 4,046,859, theentire content of which is incorporated herein by reference.

Natural zeolites may sometimes be converted to this type zeolitecatalyst by various activation procedures and other treatments such asbase exchange, steaming, alumina extraction and calcination, incombinations. Natural minerals which may be so treated includeferrierite, brew-sterite, stilbite, dachiardite, epistilbite,heulandite, and clinoptilolite. The preferred crystalline zeolites areZSM-5, ZSM-11, ZSM-12, ZSM-21, ZSM-23, ZSM-35, ZSM-38 and ZSM-48, withZSM-5 and ZSM-11 particularly preferred. In some instances, it isadvantageous to steam the frest zeolite to reduce its activity andthereby improve its selectivity prior to use. Such improvement has beennoted with steamed ZSM-5.

In a preferred aspect of this invention, the zeolites selected are thosehaving a crystal framework density, in the dry hydrogen form, of notless than about 1.6 grams per cubic centimeter. It has been found thatzeolites which satisfy all three of these criteria are most desired.Therefore, the preferred zeolites of this invention are those having aConstraint Index as defined above of about 1 to 12 and a dried crystaldensity of not less than about 1.6 grams per cubic centimeter. The drydensity for known structures may be calculated from the number ofsilicon plus aluminum atoms per 1000 cubic Angstroms, as given, e.g., onPage 19 of the article on Zeolite Structure by W. M. Meier. This paper,the entire contents of which are incorporated herein by reference, isincluded in "Proceedings of the Conference on Molecular Sieves, London,April 1967," published by the Society of Chemical Industry, London,1968. When the crystal structure is unknown, the crystal frameworkdensity may be determined by classical pyknometer techniques. Forexample, it may be determined by immersing the dry hydrogen form of thezeolite in an organic solvent not sorbed by the crystal. Or, the crystaldensity may be determined by mercury porosimetry, since mercury willfill the interstices between crystal but will not penetrate theintracrystalline free space. It is possible that the unusual sustainedactivity and stability of this class of zeolites is associated with itshigh crystal anionic framework density of not less that about 1.6 gramsper cubic centimeter. This high density must necessarily be associatedwith a relatively small amount of free space within the crystal, whichmight be expected to result in more stable structures. This free space,however, is important as the locus of catalytic activity.

Crystal framework densities of some typical zeolites including somewhich are not within the purview of this invention are:

    ______________________________________                                                        Void        Framework                                         Zeolite         Volume      Density                                           ______________________________________                                        Ferrierite      0.28 cc/cc  1.76 g/cc                                         Mordenite       .28         1.7                                               ZSM-5, 11       .29         1.79                                              ZSM-12          --          1.8                                               ZSM-23          --          2.0                                               Dachiardite     .32         1.72                                              L               .32         1.61                                              Clinoptilolite  .34         1.71                                              Laumontite      .34         1.77                                              ZSM-4, Omega    .38         1.65                                              Heulandite      .39         1.69                                              P               .41         1.57                                              Offretite       .40         1.55                                              Levynite        .40         1.54                                              Erionite        .35         1.51                                              Gmelinite       .44         1.46                                              Chabazite       .47         1.45                                              A               .5          1.3                                               Y               .48         1.27                                              ______________________________________                                    

When synthesized in the alkali metal form, the ZSM-5 type zeolite beforetreatment with BF₃ is conveniently converted to the hydrogen form,generally by intermediate formation of the ammonium form as a result ofammonium ion exchange and calcination of the ammonium form to yield thehydrogen form, i.e. HZSM-5. In addition to the hydrogen form, otherforms of the zeolite wherein the original alkali metal has been reducedto less than about 1.5 percent by weight may be used.

In practicing the desired conversion process, it may be desirable toincorporate the above-described crystalline aluminosilicate in anothermatrix resistant to temperature and other conditions employed in theprocess. However, it has been found that such incorporation preferablyshould not take place until after the zeolite has been treated withboron trifluoride since the presence of some matrices, for reasons whichare not completely understood, interferes with the activation procedure.This is particularly true for alumina (or alumina-containing) matrices.Silica matrices may not be detrimental to the activation procedure andcould be composited with the zeolite prior to activation with borontrifluoride.

The modified zeolite, if treated with BF₃ in the absence of binder, maybe incorporated with any conventional matrix material. Such matrixmaterials include synthetic or naturally occuring substances as well asinorganic materials such as clay, silica and/or metal oxides. Naturalclays which can be composited with the zeolite include those of themontmorillonite and kaolin families, which families include thesub-bentonites and the kaolins commonly known as Dixie, McNamee-Georgiaand Florida clays or others in which the main mineral constituent ishalloysite, kaolinite, dickite, nacrite or anauxite.

In addition to the foregoing materials, the zeolites employed herein maybe composited with a porous matrix material, such as alumina,silica-alumina, silica-magnesia, silica-zirconia, silica-thoria,silica-berylia, silica-titania as well as ternary compositions, such assilica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesiaand silica-magnesia-zirconia. The matrix may be in the form of a cogel.The relative proportions of zeolite component and inorganic oxide gelmatrix on an anhydrous basis may vary widely with the zeolite contentranging from between about 1 to about 99 percent by weight and moreusually in the range of about 5 to about 80 percent by weight of the drycomposite.

Although there is generally some type of correlation between alpha valueand catalytic activity in the conversions contemplated in thisinvention, the alpha activity of the boron trifluoride treated catalystwas much reduced by the treatment, but the conversion of methanol wentup (Table 1). This is a surprising and unexpected result which is notunderstood.

The following examples will illustrate the best mode contemplated forcarrying out the invention.

EXAMPLE 1

A sample of HZSM-5 having a silica-to-alumina ratio or 70:1 withoutbinder was treated with boron trifluoride by contacting it at 150° C.and at atmospheric pressure with boron trifluoride flowing at 30 cc/min.through a 1 gram catalyst bed for approximately 10 minutes, after whichthe zeolite was cooled in a steam of dry nitrogen.

EXAMPLE 2-6

The boron trifluoride modified catalyst of Example 1 was then tested forconversion of methanol to hydrocarbons along with an HZSM-5 type zeolitewhich had not been boron trifluoride modified. The following Table 1compares data from the catalyst of this invention with the catalyst ofthe prior art.

                                      TABLE 1                                     __________________________________________________________________________                                          Approximate                                                         Approximate                                                                             Activity                                                      Conversion                                                                          WHSV to Achieve                                                                         Enhancement                             Example                                                                            Catalyst                                                                             Temp, °C.                                                                    WHSV                                                                              wt. % 100% Conv.                                                                              Factor                                  __________________________________________________________________________    2    HZSM-5 300   1.2 46    0.6       --                                      3    HZSM-5 300   1.5 35    0.5       --                                      4    HZSM-5 300   6.2  7    0.5       --                                      5    BF.sub.3 HZSM-5                                                                      300   9.0 100   9.0       15-20                                   6    BF.sub.3 HZSM-5                                                                      280   2.3 100   2.3       4-5                                     __________________________________________________________________________

As can be seen from the above table, a space velocity of approximately0.5 is required to achieve 100% methanol conversion at 300° C. for auntreated HZSM-5. For the boron trifluoride modified catalyst, a spacevelocity of 9.0 achieves 100% methanol conversion. This corresponds toan increase in catalyst activity by a factor of approximately 15-20.Even at 280° C., the BF₃ modified catalyst is four to five times asactive as the unmodified catalyst at 300° C.

EXAMPLES 7-13

A series of experiments were carried out in order to demonstrate theuniqueness of the novel activation procedure of this invention.

In each of Examples 7-13, HZSM-5 having a silica-to-alumina ratio of70:1 was employed. In Examples 7 and 10, the conventional HZSM-5catalyst of the prior art was employed. In Examples 8 and 11, and HZSM-5treated with boron fluoride in the manner set forth in Examples 2-6 wasemployed.

In Example 9, an ammonium fluoride treated catalyst was employed. Thiscatalyst was prepared by mixing 0.46 gram of ammonium fluoride with 1.0gram of HZSM-5 (no binder) and heating at 150° C. for 10 minutes withargon flowing at 30 cc/min. These conditions simulate those used for thepreparation of BF₃ catalyst. The catalyst of Example 9 was then calcinedin air at 500° C. overnight to convert it to the hydrogen form. InExample 12, a mixture of HZSM-5 with alumina was treated with BF₃ in themanner previously described. In Example 13, a hydrogen fluoride treatedcatalyst was used. This catalyst was prepared by flowing a mixture of 3cc of hydrogen fluoride and 27 cc of argon at 300 cc/min. over 1 gram ofHZSM-5 (no binder) at 150° C. for 15 minutes. The results obtained formethanol conversion as well as alpha values of the various catalyst aregiven in Table 2.

                                      TABLE 2                                     __________________________________________________________________________    Conversion of Methanol Over ZSM-5 Catalysts                                   SiO.sub.2 /Al.sub.2 O.sub.3 = 70/1                                                                             Approximate                                                                          Approximate                                                      Conversion                                                                          WHSV for                                                                             Activity                              Example                                                                            Catalyst                                                                              Alpha                                                                             Temp, °C.                                                                    WHSV                                                                              Wt %  100% Conv.                                                                           Enhancement Factor                    __________________________________________________________________________    7    HZSM-5  150 280   2.3 32    0.7    --                                    8    BF.sub.3 -HZSM-5                                                                       10 280   4.5 64    2.9    4.1                                        NH.sub.4 F Treated                                                       9    HZSM-5  150 280   2.0 34    0.7    1.0.sup.(a)                           10   HZSM-5  150 300   9.0 14    1.2    --                                    11   BF.sub.3 -HZSM-5                                                                       0  300   6.0 58    3.5    2.9                                        BF.sub.3 -HZSM-5                                                         12   Binder   6  300   2.0 83    1.7    1.4                                        HF Treated                                                               13   HZSM-5   18 300   2.0 10    0.2    0.2.sup.(b)                           __________________________________________________________________________     .sup.(a) No activation relative to parent                                     .sup.(b) Deactivated relative to parent HZSM5-                           

As can be seen from the above table, the catalyst of Example 8 had asubstantially lower alpha activity than the catalyst of Example 7, yetit had enhanced activity for the conversion of methanol. The same isequally true with regard to the catalyst of Example 11 as compared tothe catalyst of Example 10. Please note that treatment with ammoniumfluoride, i.e. Example 9, and hydrogen fluoride, i.e. Example 13 did notresult in enhancement of methanol conversion activity and, in fact,Example 13 shows an actual decline relative to the untreated material.

Example 12 depicts the results of incorporating an HZSM-5 into analumina binder prior to treatment with boron trifluoride and, as can beseen, a catalyst was obtained with an alpha of 6 and only slightlyenhanced activity at 300° C. The BF₃ appears to react much more rapidlywith the alumina binder than with the ZSM-5.

EXAMPLES 14-17

These examples will illustrate the criticality of the silica-to aluminaratio of the ZSM-5 type zeolite. In Examples 14 and 15, a crystallineZSM-5 zeolite having a silica-to alumina ratio of 800:1 was employed. InExamples 16 and 17, a similar material but having a silica-to-aluminaratio of 1600:1 was employed. The method of activation with borontrifluoride was the same as previously described. The results are shownin Table 3.

                                      TABLE 3                                     __________________________________________________________________________    Conversion of Methanol Over ZSM-5 Catalysts                                                                  Approximate                                                                          Approximate                                                      Conversion                                                                          WHSV for                                                                             Activity                                Example                                                                            Catalyst                                                                            Alpha                                                                             Temp, °C.                                                                    WHSV                                                                              Wt %  100% Conv.                                                                           Enhancement Factor                      __________________________________________________________________________    14   HZSM-5.sup.(a)                                                                      14  340   4.0 76    3.0    --                                           BF.sub.3-                                                                15   HZSM-5.sup.(a)                                                                      0.5 340   4.0 56    2.2    0.7                                     16   HZSM-5.sup.(b)                                                                      7   400   10  13    1.3    --                                           BF.sub.3                                                                 17   HZSM-5.sup.(b)                                                                      1.6 390   2.0 54    1.1    0.8                                     __________________________________________________________________________     .sup.(a) SiO.sub.2 /Al.sub.2 O.sub.3 =                                        .sup.(b) SiO.sub.2 /Al.sub.2 O.sub.3 = 1600/1                            

As can be seen from the table, treatment with boron trifluoride did notenhance the methanol conversion activity of either of these two ZSM-5'ssimply because the silica-to-alumina ratio was too high.

Therefore, the novel process of this invention is applicable to ZSM-5type zeolites having a silica-to-alumina ratio of 30 to no greater thanabout 300 and, more preferably, no greater than 100 and, even moredesirably, having a silica-to-alumina ratio of from about 30 to 80.

EXAMPLE 18

A boron trifluoride modified catalyst prepared as in Example 1 wastested for propylene conversion (oligomerizaton) at 300° C. and 30 WHSV.Table 4 compares the data obtained with the boron trifluoride modifiedcatalyst with data obtained using HZSM-5 of similar activity(alpha-test) at the same operation conditions.

As can be seen from Table 4, propylene conversion was approximately 16times higher for the boron trifluoride treated catalyst compared tountreated HZSM-5. In addition, the boron trifluoride treated catalystsproduced more of desirable C₆ + gasoline range hydrocarbons. Otherolefins would be expected to react similarly to propylene.

                  TABLE 4                                                         ______________________________________                                                        BF.sub.3 --HZSM-5                                                                       HZSM-5                                              ______________________________________                                        Temperature, °C.                                                                         300         300                                             WHSV              30          30                                              Catalyst Activity,(α)                                                                     0.14        0.16                                            Conversion, wt %  99          6                                               Product distribution, wt %                                                    Methane           0.0         0.0                                             Ethane            0.0         0.0                                             Ethylene          0.2         0.0                                             Propane           3.3         1.0                                             Propylene         --          --                                              i-Butane          6.9         2.9                                             n-Butane          3.1         2.0                                             C.sub.4 Olefins   11.3        17.0                                            C.sub.5 Olefins   3.6         15.5                                            C.sub.6 Olefins   13.8        30.2                                            C.sub.7 Olefins   10.5        10.4                                            C.sub.8 Olefins   33.4        8.4                                             C.sub.9 Olefins   11.5        12.4                                            C.sub.10 Olefins  2.3         0.2                                                               99.9        100.0                                           ______________________________________                                    

EXAMPLE 19

A boron trifluoride catalyst prepared as in Example 1 was tested fortoluene disproportionation at 500° C. and 10 WHSV. Table 2 summarizesthe data and compares them with data obtained using HZSM-5 of similaractivity (alpha-test).

As can be seen from Table 5, at the same operating conditions and usingcatalysts of the same alpha-activity, the boron trifluoride catalystshowed approximately 18 times higher conversion compared to untreatedHZSM-5.

                  TABLE 5                                                         ______________________________________                                                      BF.sub.3 --HZSM-5                                                                       HZSM-5                                                ______________________________________                                        Temperature, °C.                                                                       500         500                                               WHSV            10          10                                                Catalyst Activity                                                                             2.2         2.2                                               (alpha-test)                                                                  Conversion, wt %                                                                              5.07        0.28                                              ______________________________________                                    

EXAMPLE 20

A boron trifluoride catalyst prepared as in Example 1 was tested forxylene isomerization at 10 WHSV and various temperatures. Table 6summarizes the data and compares them with data obtained using HZSM-5 ofsimilar activity (alpha-test).

As can be seen from Table 6, at 300° C. and using catalysts of the samealpha-activity, the boron trifluoride catalyst showed approximately fourtimes higher conversion compared to untreated HZSM-5. In order to obtainequivalent conversions, the temperature of the boron trifluoridecatalyst had to be significantly lowered to 230° C.

                  TABLE 6                                                         ______________________________________                                                   BF.sub.3 --HZSM-5                                                                          HZSM-5                                                ______________________________________                                        Temperature, °C.                                                                    300        230     300                                           WHSV         10         10      10                                            Catalyst Activity                                                                          2.2        2.2     2.2                                           (alpha-test)                                                                  Conversion, wt. %                                                                          16.3       4.3     4.6                                           ______________________________________                                    

For the conversions contemplated herein, it is preferred to use ZSM-5type zeolites having a silica-to-alumina ratio no greater than 300 and,more preferably, no greater than 100 and, even more desirably, having asilica-to-alumina ratio of from about 30 to 80.

In addition to the above examples, the catalysts of the invention mayalso be used in a wide variety of acid catalyzed reactions. Dewaxing,i.e., the selective cracking of wax molecules, can be carried out attemperatures greater than 175° C. (347° F.), more preferably attemperatures from 200° C. (392° F.) to 430° C. (806° F.), and even morepreferably at temperatures from 260° C. (500° F.) to 360° C. (680° F.).The dewaxing reaction can be carried out at space velocities (LHSV) from0.1 to 100, more preferably from 0.1 to 50 and at pressures up to 3000psig, more preferably from 25 to 1500 psig.

The alkylation of aromatics with alcohols or olefins may be carried outat temperatures for 150° C. to 750° C., more preferably from 225° C. to600° C., at pressures up to 1500 psig, more preferably from 20 psig to500 psig, at WHSV's form 0.1 to 400, more preferably from 3 to 30.Alcohols or olefins such as methyl alcohol, ethyl alcohol, propene,ethylene, butene, 1-butene, 1-propene, 1-dodecene, can be used.

EXAMPLE 21

Several preparations were made by the method used in Example 1 and wereevaluated for physical properties, including selectivity for ethyleneproduced when converting methanol at 100% conversion. The results aresummarized in Table 7.

                  TABLE 7                                                         ______________________________________                                        Physical                    Range for                                         Property        HZSM-5      BF.sub.3 --HZSM-5                                 ______________________________________                                        Alpha Value         150    (typical)                                                                             0 to 29                                    Crystallinity, %    100           90 to 95                                    O--xylene sorption  50             19                                         Capacity, mg/g                                                                Diffusion time for                                                            30% of capacity     270    900                                                for O--xylene, minutes                                                        Wt % Boron          0             0.1-0.5                                     Wt % Fluorine       0              5 to 10                                    Ethylene selectivity,                                                         100% Methanol       8       18                                                Conversion, wt %                                                              ______________________________________                                    

Although this invention is described particularly with reference to BF₃,it is contemplated to employ other Lewis acid fluorides such as PF₃,AsF₃, SbF₅ and BiF₅ in place of BF₃.

What is claimed is:
 1. A method for modifying a ZSM-5 type crystallinezeolite having a silica to alumina ratio of 30 to not greater than 300,which method comprises contacting said zeolite with gaseous borontrifluoride under a combination of conditions of temperature, contacttime and pressure, said combination being effective to substantiallyreduce its activity for cracking normal hexane as measured by the alphatest conducted at 538° C. and thereby forming a modified zeolitecharacterized by enhanced catalytic activity for converting methanol tohydrocarbons.
 2. The method described in claim 1 wherein saidtemperature is 25° to 500° C., and wherein said contacting is at apressure of 0.01 to 500 psig for from about 0.01 hour to about 10 hours.3. The method of claim 2 including the step of purging said contactedzeolite with an inert gas.
 4. The method of claim 1 wherein said ZSM-5type crystalline zeolite is free of alumina binder.
 5. The method ofclaim 2 wherein said ZSM-5 type crystalline zeolite is free of aluminabinder.
 6. The method described in claim 1 wherein said crystallinezeolite is HZSM-5.
 7. The method described in claim 2 wherein saidcrystalline zeolite is HZSM-5.
 8. The method described in claim 3wherein said crystalline zeolite is HZSM-5.
 9. The method described inclaim 4 wherein said crystalline zeolite is HZSM-5.
 10. The methoddescribed in claim 5 wherein said crystalline zeolite is HZSM-5.
 11. Theproduct produced by the method of claim 1 or 2 or 3 or 4 or 5 or 6 or 7or 8 or 9 or
 10. 12. In the process for the conversion of feedcompositions of alkyl alcohols having up to four carbon atoms and ethersderived therefrom wherein said feed is contacted at elevatedtemperatures and pressures with a crystalline ZSM-5 type zeolite havinga Constraint Index of about 1 to about 12 and a silica-to-alumina rationo greater than 300, the improvement which comprises treating said ZSM-5type zeolite with boron trifluoride in order to enhance its activityprior to said conversion of said feed.
 13. The process of claim 12wherein the silica-to-alumina ratio is no greater than
 100. 14. Theprocess of claim 13 wherein the silica-to-alumina ratio is between 30and
 80. 15. The process of claim 12 wherein said ZSM-5 type zeolite isZSM-5.
 16. The process of claim 13 wherein said ZSM-5 type zeolite isZSM-5.
 17. The process of claim 14 wherein said ZSM-5 type zeolite isZSM-5.
 18. The process of claim 12 wherein said feed is methanol. 19.The process of claim 13 wherein said feed is methanol.
 20. The processof claim 14 wherein said feed is methanol.
 21. The process of claim 15wherein said feed is methanol.
 22. The process of claim 16 wherein saidfeed is methanol.
 23. The process of claim 17 wherein said feed ismethanol.
 24. The modified zeolite composition produced by the method ofclaim
 1. 25. The composition described in claim 24 wherein said ZSM-5type crystalline zeolite is ZSM-5.